1. Field of the Invention
This invention relates to a solid-state image sensor such as a charge-coupled imaging device covered with a color filter, and more particularly to an improvement of the color filter.
2. Description of the Prior Art
An interline type charge-coupled area imaging device is covered with a color filter to obtain a color imaging signal. The color filter used for a single-chip CCD imaging device has yellow, cyan and green filters as filter elements which are arranged in rows and columns. By adding and subtracting between signals produced from adjacent rows, blue and red signals are separated. A green signal is synthesized from the blue and red signals and a low range luminance signal.
However, according to the arrangement of the filter elements in the prior art, some rows and columns of filter elements lacks filters detecting one of three primary colors. For example, a color filter in the prior art, first kind of rows is made of yellow filters Ye transmitting red and green light and green filters G transmitting green light which are placed alternately. Second kind of rows is made of cyan filters Cy transmitting blue and green light and green filters G which are placed alternately. The first and second kinds of rows are arranged alternately. The first kind of rows cannot detect blue light and the second kind of rows cannot detect red light. Similarly, first kind of columns having yellow filters Ye, cyan filters Cy and green filters G and second kind of columns having green filters G and cyan filters Cy are arranged alternately. The second kind of columns cannot detect red light. Therefore, fine patterns of blue and red cannot be detected, causing a poor resolution in a reproduced picture.